The present invention relates generally to monitoring and the simulateous plotting of output signals produced by transducers associated with the measurement of related operational parameters. The invention deals more specifically with machine monitoring apparatus for processing and generating in substantially real-time, simultaneous plots representative of machine member motion relative to a workpiece and the power consumed to produce the motion. The invention further specifically deals with monitoring apparatus for the selective collection, storage and subsequent retrieval of plot data, plots collectively representative of plot data and the calculation of desired machine and process parameters using the plot data.
It is known presently to monitor the operation of a machine, such as, for example, a grinding machine or other material removal/processing machine, by recording the relative movement between a machine member and a workpiece and the power consumed by the machine during the machine process. Such recordings are generally plotted on continuous rolls of recording paper using a strip chart recorder coupled to one or more transducers associated with the machine being monitored. Typically, for a grinding machine, a linear displacement transducer senses the movement of a grinding wheel relative to and generally toward and away from a work piece and generates an output voltage signal having a magnitude representative of and proportional to this relative displacement between the grinding wheel and the workpiece during a grinding cycle. A power transducer senses the power consumed in the material processing during the grinding cycle and generates an output voltage signal having a magnitude representative of and proportional to the power consumption. The voltage signals representative of displacement and power consumption are sensed and recorded by the strip chart recorder. Data corresponding to the relative displacement and power consumption is manually extracted using scales, calipers, dividers, etc. from a plot on a off-line basis, assuming such a plot was made and recorded, for the desired machine operation. The extracted data is subsequently used in accordance with known mathematical formulas to calculate the desired parameters from which the performance of the machine and the efficiency of the machine process may be determined and evaluated.
Although a conventional strip chart recorder has the capability of recording information from a number of different transducers monitoring a machine process, there are a number of limitations and disadvantages associated with its use that makes strip chart recording extremely cumbersome and generally unsatisfactory for monitoring grinding machines and the like in a typical manufacturing facility.
One problem generally associated with machine monitoring using strip chart recorders is that the monitored information is recorded and stored on relatively long strips or continuous rolls of chart paper. As a result, it is often inconvenient, difficult and tedious to review the recorded information to extract the necessary desired data for use in the computational formulas.
Another problem generally associated with monitoring using strip chart recorders is that although it is possible to sense and record transducer output signals in real-time, associated computations, analysis, etc. must generally be done after-the-fact and off-line. Accordingly, any problems that may be present and associated with the machine or machine process and which problems may affect the final product produced by the machine process may go undetected for some period of time. The delay associated in detecting such problems often results in increased costs, lower machine and process efficiency, increased machine maintenance and products having an inferior quality.
Another problem generally associated with monitoring using strip chart recorders is the difficulty and inconvenience associated with changing and tracking the calibration scales or gain of the recorder during the monitoring and recording interval. Generally, a voltage signal having a known magnitude is used to calibrate the excursion of the recording pen across the chart paper, that is, a given magnitude voltage causes the recording pen to move an associated given distance. If the gain of the strip chart recorder is changed, for example, to increase the pen excursion for a small magnitude signal or to reduce the pen excursion to stay within the limits of the recording paper for a larger magnitude signal, it is generally necessary to stop the monitoring and recording process to permit the recalibration. In addition, the point at which the recalibration or scale change is made must be recorded on the chart paper. If the scan time interval is changed to expand or compress a plot, that is, if the rate at which the chart paper is fed is increased or decreased, each new associated scan rate must also be recorded on the chart paper for off-line use in data extraction. Consequently, it is generally not possible or practical using strip chart recorders to produce data plots that are customized for a user's specific application needs. A careful and involved review of the raw-data recorded followed by complete replotting are generally necessary to obtain presentable and meaningful data when using a strip chart recorder.
A further problem generally associated with monitoring using strip chart recorders is that if a signal associated with a transducer output is not recorded on the chart paper at the time it occurs, it can not be regenerated or recaptured because the data is lost. Often during the analysis of recorded plots, it is found that data from one or more previous machine operation cycles would be useful but is not available because the output signal information was not plotted and from which plot the desired data could be extracted for analysis. Consequently, all output signal information must be sensed and recorded by the strip chart recorder at the time of machine operation to insure that all data will be available for later use if so desired.
It is desirable therefore to provide apparatus for monitoring in real-time the operation of a machine or other process that overcomes the disadvantages and the limitations generally associated with monitoring using strip chart recorders.
It is a general object of the present invention therefore to provide monitoring apparatus that overcomes the drawbacks and limitations associated with monitoring using strip chart recorders.
It is a more specific object of the present invention to provide a monitoring apparatus that is particularly suited for monitoring in real-time the output signals from a plurality of transducers which transducers sense related process or operational variables.
It is another specific object of the present invention to provide monitoring apparatus for monitoring and recording in real-time data associated with and representative of the relative displacement between a grinding wheel and a workpiece and the power consumption of a grinding machine during a grinding cycle.
It is a further object of the present invention to provide monitoring apparatus that is both portable and easily adaptable for use in monitoring a variety of grinding machines.
It is yet a further object of the present invention to provide monitoring apparatus that continuously collects data associated with the grinding machine operation for use in generating a plot of relative displacement and power consumption wherein the data is, if desired, subsequently stored electronically in digital form for processing.
It is yet a further object of the present invention to provide monitoring apparatus that recalls the stored data associated with a selected monitoring cycle and processed as a graphic representation for selective viewing on a display or on a paper print out.
It is still yet a further object of the present invention to provide monitoring apparatus for computing various grinding parameters from data electronically stored in the apparatus and related to a given grinding machine.
It is still a further object of the present invention to provide monitoring apparatus that permits the easy changing and automatic continuous tracking and identification of calibration and time scales.
Other objects, features and advantages of the present invention will be readily apparent from the following detailed description and the claims taken in conjunction with the accompanying drawings.